1. Field of the Invention
This invention relates to the field of couplings for joining abutting ends of substantially collinear lengths of pipe or the like, and more particularly to a coupling of this type that is reinforced in a particular manner. Two members, each defining half of the circumference of the joined pipes, are bolted together on diametrically opposite sides of the pipes at their abutment. A pair of parallel wings that have a non-uniform radial height depend from, and essentially completely traverse axial boundaries of the outer side of said collar half, for reinforcing the coupling.
2. Description of the Related Art
Couplings for joining end-to-end pipes are known in some variations, and typically involve two semicircular members that are placed around the two pipes and are urged together by fasteners in bolting pads that are integral with the semicircular members. The structure forms a two part collar that bears radially inwardly on the two pipes, while bridging axially over the respective pipes on both sides of the abutment. Although this structure is basically uncomplicated, there are a number of aspects of the structure that present practical problems. For example, the fasteners are typically bolts that extend through the bolting pads, which extend radially of the pipes and parallel to the bolting pad of an opposed joint member. As torque is exerted to draw the bolting pads together, the joint members can be deformed from a nominally semicircular shape conforming to the pipe.
The couplings can have coupling tangs extending inwardly toward the pipes, for engaging circumferential grooves adjacent the ends of the pipes. Similarly, the pipes can be flanged. Misalignment of these parts may warp the coupling members and allow the coupling to slip. A heavily reinforced coupling part better resists deformation, but is heavy and may waste material, and can be counterproductive because the added stiffness is such that the coupling part cannot readily deform to accommodate a pipe that does not precisely match its dimensions.
The force exerted by bolts in the coupling tabs at the ends of the clamping parts along the lateral sides of the pipe, is a force exerted parallel to a diameter of the pipe. To accommodate the possibility that the pipe may be slightly oversized or the clamp slightly undersized relative to one another, it is advantageous to provide sufficient clearance and flexibility to allow the semicircular shape of the pipe to flex open. Conversely if the pipe is oversized and/or the clamp undersized, flexibility allowing the clamp halves to pull in on the pipe improves contact between the pipe and the clamp near the bolt tabs. Thus, there are advantages to providing a coupling that is flexible in certain aspects, for example to better conform to the pipes and to permit a limited ability to flex. Thus an optimal design may be the result of trade-offs and design choices that impact the effectiveness of the coupling.
U.S. Pat. No. 1,928,316--Muto discloses a two part coupling for conduits, having a hinge joint on one lateral side of adjoining conduit or pipe ends, instead of a pair of bolting pads. On the opposite side of the pipe, the bolting pads are urged together by a bolt, for clamping the hinge parts together and thereby joining the ends of the pipe. Muto includes stiffening ribs extending in diminishing size from a clamp edge to a point approximately three-quarters around the clamp body.
U.S. Pat. Nos. 4,611,839 and 4,639,020, each to Rung et al, disclose two-part couplings having reinforcing flanges or buttresses for controlling flexing and bending of the bolting pads. However, as shown in each of the Rung et al references, the reinforcing buttresses and flanges do not continue around the full circumference portion encompassed by the coupling part.
U.S. Pat. No. 5,058,931--Bowsher discloses a circumferential pipe clamp having a raised shoulder on each edge throughout the length of the clamp. The raised shoulder is the same height throughout its length.
U.S. Pat. No. 4,17,755--Gittleman discloses a pipe coupling having annular ribs adjacent annular grooves. The annular ribs have a uniform height around the circumference portion encompassed by the coupling part.
U.S. Pat. No. 3,695,638--Blakeley discloses a pipe coupling having wings located near an end of the coupling. The wings do not continue around the circumference portion encompassed by the coupling part.
The foregoing patent references suggest that the art of clamp-like pipe couplings is well developed. However, the references do not suggest that it would be advantageous to reinforce a pipe coupling by varying the extent of the reinforcement provided by parallel wings located laterally of the coupling parts (at the axial boundaries of the coupling with respect to the pipes), such that the wings are of a different radial height from point to point along the length of the coupling, that is of differing radial height along the circumference encompassed by each of the coupling halves. According to the invention, a pipe coupling has a pair of parallel wings integral with the coupling halves, protruding radially at the lateral edges or boundaries around the portion of the semicircular arc encompassed by each coupling part or half. The wings have a relative minimum height at points spaced from the axial centerline of the pipe, and gradually increase in size towards the centerline or midpoint between the bolt tabs of the clamp, and the wings are largest at this midpoint.
The wings provide maximum reinforcement against flexing of the clamping parts where the wings are radially highest, and this occurs at the greatest distance from the bolt tabs at the ends of the coupling parts. This variation in the reinforcement and rigidity of the pipe joint members produces a dynamic balance when the opposed clamp halves are bolted together or similarly urged inwardly against the pipe ends at the coupling, and provides an optimal balance between strength and the ability to flex.